1. Field of the Invention
The present invention relates to certain substituted ethenes, specifically certain N-substituted alkyl or arylalkyl thionitroethenamines, derivatives thereof, intermediates in the production thereof and processes for the manufacture of all the aforesaid.
2. Brief Description of the Related Art
In general terms the said family of nitroethenes is known, although certain particular nitroethenes disclosed herein are believed to be novel, and have known uses as intermediates in the manufacture of pharmaceutical compounds such as the histamine H.sub.2 antagonists containing the pharmaceutically active end group --NHC(.dbd.CHNO.sub.2)NHX wherein X is an organic radical, for example niperotidine which has the formula ##STR1##
Spanish Patent Specification No. 523448 describes the preparation of N-methyl-1-methylthio-2-nitroethenamine from the dipotassium salt of 2-nitrodithioacetic acid (1-nitro-2,2-bismercapto-ethylene) by a three stage process involving firstly the methylation of one only of the KS-groups by reaction with dimethyl sulphate, secondly the conversion of the resulting CH.sub.3 S-group into a CH.sub.3 NH-- group by reaction with methylamine and thirdly, the methylation of the second KS-group by reaction with a further quantity of dimethyl sulphate. This patent is silent as to any possibility for producing other N-substituted thionitroethenamines.
The process described in the Spanish Patent requires careful control at all stages to avoid the production of unwanted reaction products such as the bis(methylthio) derivative and is disadvantageous in requiring a repetition of the dimethyl sulphate reaction due to the toxic nature of that compound.
It is known in the chemical art that, in general, amines do not react with dianions since the lone pair electrons on the amine inhibit reaction with a molecule which is already doubly negatively charged. This inhibition does not apply to dimethyl sulphate. The processing sequence of the Spanish Patent No. 523448 is therefore in accord with current belief in the art.
The present applicant has found, however, that certain amines can be made to react directly with the 2-nitrodithioacetate dianion. This has enabled a highly selective two stage process for the production of aminosubstituted thiosubstituted nitroethenes to be developed.